Asymmetric cation nonstoichiometry in spinels: Site occupancy in Co 2ZnO4 and Rh2ZnO4

Tula R. Paudel, Stephan Lany, Mayeul D'Avezac, Alex Zunger, Nicola H. Perry, Arpun R. Nagaraja, Thomas O Mason, Joanna S. Bettinger, Yezhou Shi, Michael F. Toney

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Two cations A and B in A2BO4 spinels appear in precise 2:1 Daltonian ratio ("line compounds") only at very low temperature. More typically, at finite temperature, they tend to become either A rich or B rich. Here we survey the experimentally observed stoichiometry asymmetries and describe the first-principles framework for calculating these. Defect calculations based on first principles are used to calculate the enthalpies of substitution of A atom ΔH(ATd) and B atom ΔH(BOh) and determine their site occupancies leading to (non)-stoichiometry. In Co2ZnO4, the result of the calculation for site occupancy compares well with that measured via anomalous x-ray diffraction. Further, the calculated phase boundary also compares well with that measured via Rietveld refinement of x-ray diffraction data on bulk ceramic sintered samples of Co2ZnO4 and Rh 2ZnO4. These results show that Co2ZnO 4 is heavily Co nonstoichiometric above 500C, whereas Rh 2ZnO4 is slightly Zn nonstoichiometric. We found that, in general, the calculated ΔH(ATd) is smaller than ΔH(BOh), if the A-rich competing phase is isostructural with the A2BO4 host, for example, A2AO4, whereas B-rich competing phase is not, for example, BO. This observation is used to qualitatively explain nonstoichiometry and solid solutions observed in other spinels.

Original languageEnglish
Article number064109
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number6
DOIs
Publication statusPublished - Aug 22 2011

Fingerprint

Cations
Positive ions
cations
Stoichiometry
Atoms
stoichiometry
x ray diffraction
Diffraction
atoms
X rays
Rietveld refinement
Phase boundaries
Enthalpy
Solid solutions
Substitution reactions
solid solutions
enthalpy
asymmetry
ceramics
substitutes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Paudel, T. R., Lany, S., D'Avezac, M., Zunger, A., Perry, N. H., Nagaraja, A. R., ... Toney, M. F. (2011). Asymmetric cation nonstoichiometry in spinels: Site occupancy in Co 2ZnO4 and Rh2ZnO4. Physical Review B - Condensed Matter and Materials Physics, 84(6), [064109]. https://doi.org/10.1103/PhysRevB.84.064109

Asymmetric cation nonstoichiometry in spinels : Site occupancy in Co 2ZnO4 and Rh2ZnO4. / Paudel, Tula R.; Lany, Stephan; D'Avezac, Mayeul; Zunger, Alex; Perry, Nicola H.; Nagaraja, Arpun R.; Mason, Thomas O; Bettinger, Joanna S.; Shi, Yezhou; Toney, Michael F.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 84, No. 6, 064109, 22.08.2011.

Research output: Contribution to journalArticle

Paudel, TR, Lany, S, D'Avezac, M, Zunger, A, Perry, NH, Nagaraja, AR, Mason, TO, Bettinger, JS, Shi, Y & Toney, MF 2011, 'Asymmetric cation nonstoichiometry in spinels: Site occupancy in Co 2ZnO4 and Rh2ZnO4', Physical Review B - Condensed Matter and Materials Physics, vol. 84, no. 6, 064109. https://doi.org/10.1103/PhysRevB.84.064109
Paudel, Tula R. ; Lany, Stephan ; D'Avezac, Mayeul ; Zunger, Alex ; Perry, Nicola H. ; Nagaraja, Arpun R. ; Mason, Thomas O ; Bettinger, Joanna S. ; Shi, Yezhou ; Toney, Michael F. / Asymmetric cation nonstoichiometry in spinels : Site occupancy in Co 2ZnO4 and Rh2ZnO4. In: Physical Review B - Condensed Matter and Materials Physics. 2011 ; Vol. 84, No. 6.
@article{168ab01926974d65896d42d898b15e39,
title = "Asymmetric cation nonstoichiometry in spinels: Site occupancy in Co 2ZnO4 and Rh2ZnO4",
abstract = "Two cations A and B in A2BO4 spinels appear in precise 2:1 Daltonian ratio ({"}line compounds{"}) only at very low temperature. More typically, at finite temperature, they tend to become either A rich or B rich. Here we survey the experimentally observed stoichiometry asymmetries and describe the first-principles framework for calculating these. Defect calculations based on first principles are used to calculate the enthalpies of substitution of A atom ΔH(ATd) and B atom ΔH(BOh) and determine their site occupancies leading to (non)-stoichiometry. In Co2ZnO4, the result of the calculation for site occupancy compares well with that measured via anomalous x-ray diffraction. Further, the calculated phase boundary also compares well with that measured via Rietveld refinement of x-ray diffraction data on bulk ceramic sintered samples of Co2ZnO4 and Rh 2ZnO4. These results show that Co2ZnO 4 is heavily Co nonstoichiometric above 500C, whereas Rh 2ZnO4 is slightly Zn nonstoichiometric. We found that, in general, the calculated ΔH(ATd) is smaller than ΔH(BOh), if the A-rich competing phase is isostructural with the A2BO4 host, for example, A2AO4, whereas B-rich competing phase is not, for example, BO. This observation is used to qualitatively explain nonstoichiometry and solid solutions observed in other spinels.",
author = "Paudel, {Tula R.} and Stephan Lany and Mayeul D'Avezac and Alex Zunger and Perry, {Nicola H.} and Nagaraja, {Arpun R.} and Mason, {Thomas O} and Bettinger, {Joanna S.} and Yezhou Shi and Toney, {Michael F.}",
year = "2011",
month = "8",
day = "22",
doi = "10.1103/PhysRevB.84.064109",
language = "English",
volume = "84",
journal = "Physical Review B-Condensed Matter",
issn = "1098-0121",
publisher = "American Physical Society",
number = "6",

}

TY - JOUR

T1 - Asymmetric cation nonstoichiometry in spinels

T2 - Site occupancy in Co 2ZnO4 and Rh2ZnO4

AU - Paudel, Tula R.

AU - Lany, Stephan

AU - D'Avezac, Mayeul

AU - Zunger, Alex

AU - Perry, Nicola H.

AU - Nagaraja, Arpun R.

AU - Mason, Thomas O

AU - Bettinger, Joanna S.

AU - Shi, Yezhou

AU - Toney, Michael F.

PY - 2011/8/22

Y1 - 2011/8/22

N2 - Two cations A and B in A2BO4 spinels appear in precise 2:1 Daltonian ratio ("line compounds") only at very low temperature. More typically, at finite temperature, they tend to become either A rich or B rich. Here we survey the experimentally observed stoichiometry asymmetries and describe the first-principles framework for calculating these. Defect calculations based on first principles are used to calculate the enthalpies of substitution of A atom ΔH(ATd) and B atom ΔH(BOh) and determine their site occupancies leading to (non)-stoichiometry. In Co2ZnO4, the result of the calculation for site occupancy compares well with that measured via anomalous x-ray diffraction. Further, the calculated phase boundary also compares well with that measured via Rietveld refinement of x-ray diffraction data on bulk ceramic sintered samples of Co2ZnO4 and Rh 2ZnO4. These results show that Co2ZnO 4 is heavily Co nonstoichiometric above 500C, whereas Rh 2ZnO4 is slightly Zn nonstoichiometric. We found that, in general, the calculated ΔH(ATd) is smaller than ΔH(BOh), if the A-rich competing phase is isostructural with the A2BO4 host, for example, A2AO4, whereas B-rich competing phase is not, for example, BO. This observation is used to qualitatively explain nonstoichiometry and solid solutions observed in other spinels.

AB - Two cations A and B in A2BO4 spinels appear in precise 2:1 Daltonian ratio ("line compounds") only at very low temperature. More typically, at finite temperature, they tend to become either A rich or B rich. Here we survey the experimentally observed stoichiometry asymmetries and describe the first-principles framework for calculating these. Defect calculations based on first principles are used to calculate the enthalpies of substitution of A atom ΔH(ATd) and B atom ΔH(BOh) and determine their site occupancies leading to (non)-stoichiometry. In Co2ZnO4, the result of the calculation for site occupancy compares well with that measured via anomalous x-ray diffraction. Further, the calculated phase boundary also compares well with that measured via Rietveld refinement of x-ray diffraction data on bulk ceramic sintered samples of Co2ZnO4 and Rh 2ZnO4. These results show that Co2ZnO 4 is heavily Co nonstoichiometric above 500C, whereas Rh 2ZnO4 is slightly Zn nonstoichiometric. We found that, in general, the calculated ΔH(ATd) is smaller than ΔH(BOh), if the A-rich competing phase is isostructural with the A2BO4 host, for example, A2AO4, whereas B-rich competing phase is not, for example, BO. This observation is used to qualitatively explain nonstoichiometry and solid solutions observed in other spinels.

UR - http://www.scopus.com/inward/record.url?scp=80052360173&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80052360173&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.84.064109

DO - 10.1103/PhysRevB.84.064109

M3 - Article

AN - SCOPUS:80052360173

VL - 84

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 6

M1 - 064109

ER -